From your OP I assume you're seated while meditating? One thing I know is if I allow myself to slouch forward it shallows out breathing and can lead to drowsiness.

Also if I let go of breath and just attend awareness itself I get a lot of HI and my hearing also becomes very attenuated. Even the click when the thermostat kicks in resonates through my whole being. I think it's gamma synchronicity and to me it's a very disembodied reality.

But yeah, I think there's a very fine line between that kind of meditation and a WILD, though the few attempts I made at WILD I just can't get the same state of mind laying on my back. Go figure...